Conversion of hydrocarbons



AWE}! 9 1944- H. R. WARRICK ,345,995

CONVERS ION OF HYDROCARBONS Filed Nov. 22, 1941 2 Sheets-Sheet l '2 o w b] a: w n.

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HALSTED RWARRICK INVENTOR HIS AT TORNEYS Apml 4, 1944. H. R. WARRICK CONVERSION OF HYDROCARBONS Filed Nov. 22, 1941 2 SheetsSheet 2 INVENTOR HALSTED RWARRICK m EN E23 02206 10 J mmIF Patented Apr. 4, 1944 CONVERSION OF HYDROCARBONS Halsted Rogers Warrick, West Englewood; N. J., assignor to The Texas Company, New York, N. Y., a corporation 01' Delaware Application November 22, 1941, Serial No. 420,054

5 Claims.

This invention relates to the conversion of hydrocarbons for the production of gasoline or motor fuel of high antiknock quality.

The invention contemplates certain improve- I ments in the catalytic conversion of hydrocarbons. In the catalytic cracking of hydrocarbon oils it is common practice to charge the hydrocarbons to a catalytic cracking chamber and continue the operation for a period 01 time until the catalyst has become partially spent or of reduced activity at which time the charge is diverted to another catalytic cracking chamber and a regenerating gas is introduced to the first chamber to accomplish reactivation of the catalyst. In accordance with my invention catalytic material is employed which is adapted to function not only as a cracking catalyst for the conversion of higher boiling hydrocarbons into lower boiling ones but also as an isomerization catalyst to efiect isomerization of hydrocarbons and the catalyst which has become partially spent or of reduced activity in the cracking or conversion of higher boiling hydrocarbons into lower boiling ones'is utilized, prior to any regeneration thereof, in eilecting the isomerization of hydrocarbons. In the catalytic conversion into lower boiling hydrocarbons a deposit is formed on the "catalyst which reduces the activity thereof and generally speaking the longer the operation is I jcontinued on-stream the greater will be the reduction in activity of the catalyst, so that from a practical standpoint it is necessary to terminate the operation when the catalyst is partially spent. My invention takes advantage of the fact that this partially spent catalyst is highly reactive to accomplish the isomerlzation of hydrocarbons, and it enables the utilization of catalyst, which is no longer adapted for the efiicient conversion of hydrocarbons into lower boiling products, in an isomerizing reaction to produce products 01' high antiknock quality.

In practicing the invention hydrocarbon oil such as gas oil is charged to a catalytic cracking chamber and the operation continued for a time until the catalyst has become partially spent, whereupon the charge is diverted to another catalytic cracking chamber and a gasoline or naphtha stock, such as a product of thermal cracking, which it is desired to treat for increasing the antiknock quality, is charged to the first catalytic chamber and subjected to isomerization. By having a minimum of three catalyst chambers a continuous operation may be conducted so as to simultaneously carry on catalytic cracking in one chamber. catalytic isomerization in another and regeneration of the catalyst in the. third chamber.

My invention contemplates further a combination catalytic conversion and thermal conversion process in which hydrocarbon oil is subjected to catalytic cracking, the resultant cracked products fractionated to separate higher boiling constituents from the lighter products, such higher boiling constituents subjected to thermal cracking and light products recovered from the thermally cracked products subjected to catalytic isomerization.

For the purposeof explaining the invention in detail reference is now had to the accompanying drawings wherein: V

Fig. 1 is a graph showing the relationship of time of reaction to gasoline yield in catalytic crackin Fig. 2 is a how diagramillustrating a particular example of the invention involving catalytic cracking, thermal cracking and isomerization.

Fig. 1 represents a typical curve based on the catalytic cracking of gas oil at a temperature of 960 F. with a space velocity of 2 in which the time expressed in hours on stream is plotted against the volum per cent of gasoline yield based on the total throughput. It will be observed that as the time on stream is increased the yield diminishes. In actual practice it has been found that the most economical processing period lies in the range of from 10 minutes to 4 hours. Obviously, when using these relatively short processing periods the catalyst still retains considerable activity.

In the isomerlzation reaction the catalyst does not deteriorate in activity at anything like the rate at which its activity is reduced in catalytic cracking. For example, in isomerizing thermally cracked gasoline the operation may be continued for periods approximating 24 hours tvithout any material reduction in the antiknock quality of the gasoline product. Furthermore, the catalyst which has become partially spent in the catalytic conversion of higher boiling hydrocarbons into lower boiling ones, functions satisfactorily to effect the isomerization or isoforming of gasoline constituents. Accordingly,

in the practice of the invention the catalytic conversion into lower boiling products is carried on in one chamber for a period until it is no longer economical or advantageous to continue the operation, whereupon the catalytic cracking operation is diverted to another chamber and a gasoline stock is then brought into contact with the partially spent catalyst in the first chamber and subjected to isomerlzation or isoforming.

Referring now to Fig. 2, charging stock for catalytic cracking is introduced by a pump it] to a heating coil ll disposed in a furnace 12, wherein the oil is raised to the temperature desired for catalytic cracking, and the heated oil is passed through a transfer line l3 having branch lines I3a, I3!) and [30 extending, respectively, to catalytic cracking chambers A, B and C. Each of the catalytic cracking chambers contains a bed or plurality of beds of catalytic material. The products of the catalytic cracking are withdrawn from the several chambers through lines l4a, Nb and Ho, respectively, thence through a common draw-off line H extending to a separating or fractionating chamber ii. The products of the catalytic cracking operation, as well as the products of the isomerization operation, as will appear hereinafter, are subjected to fractionation in the fractionator i5 to separate lighter products from the higher boiling products of reaction. The overhead vapors from the tower i5 pass to a condenser coil [6, thence to a receiving drum or gas separator l1 wherein the distillate is collected. The distillate may be directed by a pump l8 to a rectifying tower i9 wherein it is subjected to rectification to produce a stabilized product, the light products of undesired volatility, ordinarily essentially normally gaseous hydrocarbons, are removed through a gas line and the rectified distillate-prodnot is withdrawn through a line 2|.

The higher boiling products separated out in fractionator i5 are withdrawn by a pump 22 and are directed through a line 23 to a heating coil 24 disposed in a furnace 25 wherein the oil is heated to a cracking temperature to effect thermal cracking. If desired, additional charging stock from an extraneous source may be introduced by a pump 26 through charging line 21 to the thermal cracking operation. The heated products from the coil 24 pass through a transfer line 28 to a separator or reaction chamber 29 wherein separation of vapors from residue takes place. The residue may be withdrawn through a line 30 while separated vapors pass through vapor line 3i to a fractionating tower 32. The vapors are fractionated in the tower 32 to separate higher boiling reflux condensate from lighter vapors including gasoline constituents, and the reflux condensate is directed by a pump 33 and line 34 to the heating coil 24.

Th cracked gasoline product from the tower 32 may be passed directly to the isomerization unit. It is preferable, however, to subject the asoline constituents to treatment with a solid adsorptive catalytic material prior to passage to the isomerization unit so as to effect the removal of the highly reactive diolefins or unstable gum forming constituents. For this purpose the gasoline vapors pass from the tower 32 through a line 35 to a treating chamber 36 containing suitable polymerizing catalysts such as fuller's earth to effect the removal of the unstable hydrocarbons. The resultant polymers are withdrawn through a line 31 while the treated vapors pass through a line 38 to an after-fractionator 39 for the purpose of removing entrained polymers or higher boiling constituents. The higher boiling products fractionated out in tower 39 are withdrawn through a, line 40. The lines 31 and 40 may communicate with a common line 4i by which the polymers or higher boiling products may be conducted to the fractionator 32. The gasoline constituents pass from the tower 33 as vapors to a condenser coil 42 thence to a receiving drum or gas-separator 43 wherein the gasoline distillate is collected for the isomerizing treatment. The after-fractionator 39 may, if desired, be eliminated and an adequate separation of entrained polymers accomplished by passing the vapors from the clay chamber tower through a mist separator. oline or naphtha distillate resulting from the thermal cracking operation is withdrawn from the accumulating drum 43 and directed by a pump 44 through a line 43 to a heating coil 40 disposed in a furnace 41 wherein the gasoline constituents are heated to a temperature adapted for isomerization or insoforming. Since the thermal cracking operation is normally conducted under pressures considerably in excess of the pressure required for isoforming the pump 44 may frequently be eliminated, the distillate from the thermal cracking operation being collected under a suitable pressure higher than that used in the isoforming so that it may be fed through a control valve to the isoforming unit. If desired, the cracked naphtha may be debutanized or depentanized prior to being directed to the isomerization operation. The heated products from the coil 40 pass through a transfer line 48 having branch lines 48a, 48b and 48c communicating with the catalyst chambers A, B and C, respectively.

A pump 49 and charging line 50 is indicated for charging extraneous naphtha to the heating coil 46 for catalytic isomerization. For example, coke still naphtha produced in the coking of petroleum residual stocks may be raised in octane number by being charged to the isomerization operation. 7

A suitable oxidizing or regenerating gas such as air and flue gas is introduced through a line 5i having branch lines 5la, 51b and Sic communicating, respectively, with the catalyst chambers A, B and C and the reactivating gases are withdrawn through lines 52a, 52b and He, respectively.

The catalyst cases A, B and C are charged with a solid catalytic material adapted to function as a cracking catalyst as well as an isomerization catalyst. Natural or synthetic alumina and silica-alumina mixtures in either the crystalline or amorphous form may be employed in the practice of the invention. Various acid-treated and metal-substituted clays such as the Super- Filtrols and acid-treated and metal-substituted natural or artificial zeolites, such as the synthetic zeolite known as Doucll may be employed. Various metals such as uranium, molybdenum, manganese, lead, zinc, zirconium. thorium, nickel and the like, may be substituted in the clays or zeolites. Likewise the combination of certain acidtreated active clays of the character of Filtrol, together with added proportions of alumina or silica or both may be employed. The synthetic alumina catalysts can be improved by the addition of other constituents such as zirconium oxide or molybdenum oxide.

In practicing the invention the heated stream from the heating coil II is directed to one of the catalyst chambers containing fresh catalyst or catalyst which has been regenerated while simultaneously theheated naphtha stock from the heating coil 46 is passed to another catalyst chamber and during the period that these two chambers are on stream for catalytic cracking and isomerization respectively the other chamber during the 4 hour period and simultaneously the stream from heating coil 46 is directed to chamber B which contains catalyst which had been employed in the preceding period for catalytic cracking and isomerization is carried on in chamber B, while in chamber C catalyst which had previously been used first for catalytic cracking and then for isomerization is regenerated. In the next 4 hour period the stream from the heating coil II is diverted to chamber 0, the stream from the heating coil 46 is diverted to chamber A and the catalyst in chamber B is re generated. And the process is continued in this manner changing the catalyst chamber every 4 hours. Since the isomerization of the cracked naphtha stock can normally be carried on with the same catalyst without material drop in the octane number of the productfor a longer time than is suitable for the catalytic cracking operation, longer periods on stream in the isomerization operation may be maintained by increasing the number of catalyst chambers. However, the operation with only the three chambers will be found to be satisfactory since the isomerization operation is conducted with more or less spent catalyst which would otherwise have to be revivifled after the catalytic cracking operatiofi.

The charging stock to the catalytic cracking operation is heated in the coil II to vaporize it and raise it to a cracking temperature and it is delivered to the catalyst chamber at temperatures of the order of 900 F. and 1000 F. Best results are obtained with low pressures below 100 lbs. and preferably only moderately above atmospheric pressure.

The thermal cracking operation may be carried on under any of the usual conditions of time, temperature and pressure which are adapted for thermal cracking. For the cracking or the higher boiling products from the catalytic cracking operation temperatures in excess of 850 F. and preierably upwards of 900 F. with pressures of 200-600 lbs. are recommended.

For isomerizing the cracked naphtha temperatures of upwards of 900 F. under relatively low pressures preferably approximating atmospheric pressure are recommended.

In an example of the invention the catalyst chambers are charged with a calcined mixture of precipitated silica and alumina containing a.

small proportion'of zirconia. Straight run gas oil is heated and delivered to one of the catalyst chambers at a temperature of 960 F. and sub- Jected to catalytic cracking therein under a gauge pressure of about lbs. The higher boiling product obtained in iractionating the products of the catalytic conversion is subjected to thermal cracking at a temperature of 975 F. under 400 lbs. pressure. The thermally cracked products are separated into vapors and residue and the vapors fractionated to separate higher boiling reflux condensate from naphtha vapors. Thehigher boiling reflux condensate is cycled to the thermal cracking zone. The cracked naphtha vapors are treated with fullers earth at a 138,111? perature of 450 F. to effect polymerization of unstable gum-forming constituents and the treated naphtha is heated and delivered to the isomerization catalyst chamber at a temperature of 950 F. wherein isomerization is carried on under a gauge pressure of about 15 lbs. The operation is conducted under a time cycle of 4 hours. In other words. at the end of each 4'hour period the gas oil charge is diverted to another chamber containing regenerated catalyst and the thermally cracked naphtha is charged to the chamber containing the partially spent catalyst employed in the catalytic cracking of the gas oil in the preceding period, while the chamber containing the catalyst used for isomerization in the preceding period is regenerated and prepared for the subsequent catalytic cracking of the gas oil. The combined products from the isomerization and cataytic crackingv operations are fractionated to recover a 400 F. end point gasoline which is subjected to rectification.

In an alternative operation contemplated by the invention the reflux condensate higher boiling than gasoline, instead of being cycled to the thermal cracking unit, may be combined with the extraneous gas oil charge passing to the catalytic cracking operation, or in another advantageous operation the cracked .vapors may be fractionated to form lighter and heavier reflux condensates higher boiling than gasoline and the higher boiling fraction cycled to the thermal cracking operationwhile the lower boiling fraction is directed to the catalytic cracking operation.

The isomerization treatment of the cracked naphtha serves to raise the octane number about 5 points or more. The increase in octane number is particularly marked when taken on a road basis. For example, the octane number of coke still naphtha may be increased some 10 points as determined by the Cooperative Fuel Research Motor method and on a road basis some 14 points. The combination'of catalytic cracking and thermal cracking with the isomerization of the thermally cracked naphtha thus functions to produce a high yield of high octane number gasoline.

Although a preferred embodiment of the invention has been described herein, it will be understood that various changes and modifications may be made therein, while securing to a greater or less extent some or all of the benefits of the invention, without departing from the spirit and and subjecting said lighter fraction to isomerization in the presence of partially spent catalytic material previously usedin catalytic cracking.

2. In the catalytic conversion of hydrocarbon oils the process that comprises charging hydrocarbon oil to a reaction chamber containing a cracking catalyst wherein the oil is subjected to cracking temperature in the presence of the catalyst to eiiect catalytic conversion into lower boiling hydrocarbons and continuing the operation until the catalyst is partially spent, then diverting the charging oil to a second reaction chamber containing a cracking catalyst wherein the oil is subjected to a cracking temperature in the presence of a catalyst to effect conversion into lower boiling hydrocarbons and charging a gasoline stock to the first reaction chamber and subjecting the gasoline stock to an isomerization temperature in the presence r said partially spent catalytic material.

3. In the catalytic conversion of hydrocarbon oils the process that comprises charging hydrocarbon oil to a reaction cracking chamber containing a cracking catalyst wherein the oil is subjected to cracking temperature in the presence of the catalyst to effect catalytic conversion into lower boiling hydrocarbons and continuing the operation until the catalyst is partially spent, then diverting the charging oil to a second reaction chamber containing a cracking catalyst wherein the oil is subjected to a cracking temperature in the presence of the catalyst to effect conversion into lower boiling hydrocarbons and charging a gasoline stock to the first reaction chamber wherein it is subjected to an isomerization temperature in the presence of the partially spent catalyst, subsequently diverting the charging oil from said second reaction chamber to another reaction chamber and diverting the gasoline stock from the first reaction chamber to the second and passing a regenerating fluid through the first reaction chamber to regenerate the catalyst and adapt it for further catalytic crack- 4. In the catalytic conversion of hydrocarbon oils the method of subjecting a higher boiling stock to catalytic cracking to etIect conversion into lower boiling products and of subjecting a gasoline stock to catalytic isomerization, in a plurality of reaction chambers containing solid catalytic material, that comprises passing the higher boiling stock through one of said reaction chambers'in contact with the catalytic material therein, maintaining a temperature adapted for catalytic cracking in said reaction chamber, continuing the flow of the higher boiling stock through said reaction chamber for a period of time until the catalytic material is partially spent, thereupon diverting the higher boiling stock to another of said reaction chambers and passing the gasoline stock through the'flrst-mentioned reaction chamber in contact with the partially spent catalytic material therein, maintaining a temperature adapted for isomerization in the, first reaction chamber, and a temperature adapted for catalytic cracking, in the. second reaction chamber, continuing the latter catalytic cracking and isomerization operations until the catalytic material in the second reaction chamber is partially spent and thereupon diverting the flow of the higher boiling stock from the second reaction chamber and diverting the flow of the gasoline stock from the first reaction chamber to the sec- 0nd.

5. In the catalytic conversion of hydrocarbon oils the method of subjecting a higher boiling stock to catalytic cracking to eflect conversion into lower boiling products and or subjecting a gasoline stock to catalytic isomerization, in a plurality of reaction chambers containing solid catalytic material, that comprises passing the higher boiling stock through one of said reaction chambers in contact with the catalytic material therein, maintaining a temperature adapted for catalytic cracking in said reaction chamber, continuing use flow of the higher boiling stock through said reaction chamberior a period of time until the catalytic material is partially spent, thereupon diverting the higher boiling stock to another of said reaction chambers and passing the gasoline stock through the first-mentioned reaction chamber in contact with the partially spent catalytic material therein, maintaining a temperature adapted for isomerization in the first reaction chamber and a temperature adapted for catalytic cracking in the second reaction chamber, continuing the latter catalytic cracking and isomerization operations until the catalytic material in the second reaction chamber is partially spent and thereupon diverting the flow of the higher boiling stock from the second reaction chamber and diverting the flow of the gasoline stock from the first reaction chamber to the second and regenerating the catalytic material in each of the reaction chambers following the isomerization step therein.

' HAISTED ROGERS WARRICK. 

